/*
 * NB - This file is a modified version of one by Eric Young.
 * It was modifed by jimmikaelkael <jimmikaelkael@wanadoo.fr>
 */

/* Copyright (C) 1995 Eric Young (eay@mincom.oz.au)
 * All rights reserved.
 *
 * This file is part of an SSL implementation written
 * by Eric Young (eay@mincom.oz.au).
 * The implementation was written so as to conform with Netscapes SSL
 * specification.  This library and applications are
 * FREE FOR COMMERCIAL AND NON-COMMERCIAL USE
 * as long as the following conditions are aheared to.
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.  If this code is used in a product,
 * Eric Young should be given attribution as the author of the parts used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    This product includes software developed by Eric Young (eay@mincom.oz.au)
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

#define c2l(c, l) (l = ((unsigned int)(*((c)++))),        \
                   l |= ((unsigned int)(*((c)++))) << 8,  \
                   l |= ((unsigned int)(*((c)++))) << 16, \
                   l |= ((unsigned int)(*((c)++))) << 24)

#define l2c(l, c) (*((c)++) = (unsigned char)(((l)) & 0xff),       \
                   *((c)++) = (unsigned char)(((l) >> 8) & 0xff),  \
                   *((c)++) = (unsigned char)(((l) >> 16) & 0xff), \
                   *((c)++) = (unsigned char)(((l) >> 24) & 0xff))

#define ITERATIONS           16
#define HPERM_OP(a, t, n, m) ((t) = ((((a) << (16 - (n))) ^ (a)) & (m)), \
                              (a) = (a) ^ (t) ^ (t >> (16 - (n))))

static const unsigned int des_SPtrans[8][64] = {
    /* nibble 0 */
    {
        0x00820200, 0x00020000, 0x80800000, 0x80820200,
        0x00800000, 0x80020200, 0x80020000, 0x80800000,
        0x80020200, 0x00820200, 0x00820000, 0x80000200,
        0x80800200, 0x00800000, 0x00000000, 0x80020000,
        0x00020000, 0x80000000, 0x00800200, 0x00020200,
        0x80820200, 0x00820000, 0x80000200, 0x00800200,
        0x80000000, 0x00000200, 0x00020200, 0x80820000,
        0x00000200, 0x80800200, 0x80820000, 0x00000000,
        0x00000000, 0x80820200, 0x00800200, 0x80020000,
        0x00820200, 0x00020000, 0x80000200, 0x00800200,
        0x80820000, 0x00000200, 0x00020200, 0x80800000,
        0x80020200, 0x80000000, 0x80800000, 0x00820000,
        0x80820200, 0x00020200, 0x00820000, 0x80800200,
        0x00800000, 0x80000200, 0x80020000, 0x00000000,
        0x00020000, 0x00800000, 0x80800200, 0x00820200,
        0x80000000, 0x80820000, 0x00000200, 0x80020200},
    /* nibble 1 */
    {
        0x10042004, 0x00000000, 0x00042000, 0x10040000,
        0x10000004, 0x00002004, 0x10002000, 0x00042000,
        0x00002000, 0x10040004, 0x00000004, 0x10002000,
        0x00040004, 0x10042000, 0x10040000, 0x00000004,
        0x00040000, 0x10002004, 0x10040004, 0x00002000,
        0x00042004, 0x10000000, 0x00000000, 0x00040004,
        0x10002004, 0x00042004, 0x10042000, 0x10000004,
        0x10000000, 0x00040000, 0x00002004, 0x10042004,
        0x00040004, 0x10042000, 0x10002000, 0x00042004,
        0x10042004, 0x00040004, 0x10000004, 0x00000000,
        0x10000000, 0x00002004, 0x00040000, 0x10040004,
        0x00002000, 0x10000000, 0x00042004, 0x10002004,
        0x10042000, 0x00002000, 0x00000000, 0x10000004,
        0x00000004, 0x10042004, 0x00042000, 0x10040000,
        0x10040004, 0x00040000, 0x00002004, 0x10002000,
        0x10002004, 0x00000004, 0x10040000, 0x00042000},
    /* nibble 2 */
    {
        0x41000000, 0x01010040, 0x00000040, 0x41000040,
        0x40010000, 0x01000000, 0x41000040, 0x00010040,
        0x01000040, 0x00010000, 0x01010000, 0x40000000,
        0x41010040, 0x40000040, 0x40000000, 0x41010000,
        0x00000000, 0x40010000, 0x01010040, 0x00000040,
        0x40000040, 0x41010040, 0x00010000, 0x41000000,
        0x41010000, 0x01000040, 0x40010040, 0x01010000,
        0x00010040, 0x00000000, 0x01000000, 0x40010040,
        0x01010040, 0x00000040, 0x40000000, 0x00010000,
        0x40000040, 0x40010000, 0x01010000, 0x41000040,
        0x00000000, 0x01010040, 0x00010040, 0x41010000,
        0x40010000, 0x01000000, 0x41010040, 0x40000000,
        0x40010040, 0x41000000, 0x01000000, 0x41010040,
        0x00010000, 0x01000040, 0x41000040, 0x00010040,
        0x01000040, 0x00000000, 0x41010000, 0x40000040,
        0x41000000, 0x40010040, 0x00000040, 0x01010000},
    /* nibble 3 */
    {
        0x00100402, 0x04000400, 0x00000002, 0x04100402,
        0x00000000, 0x04100000, 0x04000402, 0x00100002,
        0x04100400, 0x04000002, 0x04000000, 0x00000402,
        0x04000002, 0x00100402, 0x00100000, 0x04000000,
        0x04100002, 0x00100400, 0x00000400, 0x00000002,
        0x00100400, 0x04000402, 0x04100000, 0x00000400,
        0x00000402, 0x00000000, 0x00100002, 0x04100400,
        0x04000400, 0x04100002, 0x04100402, 0x00100000,
        0x04100002, 0x00000402, 0x00100000, 0x04000002,
        0x00100400, 0x04000400, 0x00000002, 0x04100000,
        0x04000402, 0x00000000, 0x00000400, 0x00100002,
        0x00000000, 0x04100002, 0x04100400, 0x00000400,
        0x04000000, 0x04100402, 0x00100402, 0x00100000,
        0x04100402, 0x00000002, 0x04000400, 0x00100402,
        0x00100002, 0x00100400, 0x04100000, 0x04000402,
        0x00000402, 0x04000000, 0x04000002, 0x04100400},
    /* nibble 4 */
    {
        0x02000000, 0x00004000, 0x00000100, 0x02004108,
        0x02004008, 0x02000100, 0x00004108, 0x02004000,
        0x00004000, 0x00000008, 0x02000008, 0x00004100,
        0x02000108, 0x02004008, 0x02004100, 0x00000000,
        0x00004100, 0x02000000, 0x00004008, 0x00000108,
        0x02000100, 0x00004108, 0x00000000, 0x02000008,
        0x00000008, 0x02000108, 0x02004108, 0x00004008,
        0x02004000, 0x00000100, 0x00000108, 0x02004100,
        0x02004100, 0x02000108, 0x00004008, 0x02004000,
        0x00004000, 0x00000008, 0x02000008, 0x02000100,
        0x02000000, 0x00004100, 0x02004108, 0x00000000,
        0x00004108, 0x02000000, 0x00000100, 0x00004008,
        0x02000108, 0x00000100, 0x00000000, 0x02004108,
        0x02004008, 0x02004100, 0x00000108, 0x00004000,
        0x00004100, 0x02004008, 0x02000100, 0x00000108,
        0x00000008, 0x00004108, 0x02004000, 0x02000008},
    /* nibble 5 */
    {
        0x20000010, 0x00080010, 0x00000000, 0x20080800,
        0x00080010, 0x00000800, 0x20000810, 0x00080000,
        0x00000810, 0x20080810, 0x00080800, 0x20000000,
        0x20000800, 0x20000010, 0x20080000, 0x00080810,
        0x00080000, 0x20000810, 0x20080010, 0x00000000,
        0x00000800, 0x00000010, 0x20080800, 0x20080010,
        0x20080810, 0x20080000, 0x20000000, 0x00000810,
        0x00000010, 0x00080800, 0x00080810, 0x20000800,
        0x00000810, 0x20000000, 0x20000800, 0x00080810,
        0x20080800, 0x00080010, 0x00000000, 0x20000800,
        0x20000000, 0x00000800, 0x20080010, 0x00080000,
        0x00080010, 0x20080810, 0x00080800, 0x00000010,
        0x20080810, 0x00080800, 0x00080000, 0x20000810,
        0x20000010, 0x20080000, 0x00080810, 0x00000000,
        0x00000800, 0x20000010, 0x20000810, 0x20080800,
        0x20080000, 0x00000810, 0x00000010, 0x20080010},
    /* nibble 6 */
    {
        0x00001000, 0x00000080, 0x00400080, 0x00400001,
        0x00401081, 0x00001001, 0x00001080, 0x00000000,
        0x00400000, 0x00400081, 0x00000081, 0x00401000,
        0x00000001, 0x00401080, 0x00401000, 0x00000081,
        0x00400081, 0x00001000, 0x00001001, 0x00401081,
        0x00000000, 0x00400080, 0x00400001, 0x00001080,
        0x00401001, 0x00001081, 0x00401080, 0x00000001,
        0x00001081, 0x00401001, 0x00000080, 0x00400000,
        0x00001081, 0x00401000, 0x00401001, 0x00000081,
        0x00001000, 0x00000080, 0x00400000, 0x00401001,
        0x00400081, 0x00001081, 0x00001080, 0x00000000,
        0x00000080, 0x00400001, 0x00000001, 0x00400080,
        0x00000000, 0x00400081, 0x00400080, 0x00001080,
        0x00000081, 0x00001000, 0x00401081, 0x00400000,
        0x00401080, 0x00000001, 0x00001001, 0x00401081,
        0x00400001, 0x00401080, 0x00401000, 0x00001001},
    /* nibble 7 */
    {
        0x08200020, 0x08208000, 0x00008020, 0x00000000,
        0x08008000, 0x00200020, 0x08200000, 0x08208020,
        0x00000020, 0x08000000, 0x00208000, 0x00008020,
        0x00208020, 0x08008020, 0x08000020, 0x08200000,
        0x00008000, 0x00208020, 0x00200020, 0x08008000,
        0x08208020, 0x08000020, 0x00000000, 0x00208000,
        0x08000000, 0x00200000, 0x08008020, 0x08200020,
        0x00200000, 0x00008000, 0x08208000, 0x00000020,
        0x00200000, 0x00008000, 0x08000020, 0x08208020,
        0x00008020, 0x08000000, 0x00000000, 0x00208000,
        0x08200020, 0x08008020, 0x08008000, 0x00200020,
        0x08208000, 0x00000020, 0x00200020, 0x08008000,
        0x08208020, 0x00200000, 0x08200000, 0x08000020,
        0x00208000, 0x00008020, 0x08008020, 0x08200000,
        0x00000020, 0x08208000, 0x00208020, 0x00000000,
        0x08000000, 0x08200020, 0x00008000, 0x00208020}};
static const unsigned int des_skb[8][64] = {
    /* for C bits (numbered as per FIPS 46) 1 2 3 4 5 6 */
    {
        0x00000000, 0x00000010, 0x20000000, 0x20000010,
        0x00010000, 0x00010010, 0x20010000, 0x20010010,
        0x00000800, 0x00000810, 0x20000800, 0x20000810,
        0x00010800, 0x00010810, 0x20010800, 0x20010810,
        0x00000020, 0x00000030, 0x20000020, 0x20000030,
        0x00010020, 0x00010030, 0x20010020, 0x20010030,
        0x00000820, 0x00000830, 0x20000820, 0x20000830,
        0x00010820, 0x00010830, 0x20010820, 0x20010830,
        0x00080000, 0x00080010, 0x20080000, 0x20080010,
        0x00090000, 0x00090010, 0x20090000, 0x20090010,
        0x00080800, 0x00080810, 0x20080800, 0x20080810,
        0x00090800, 0x00090810, 0x20090800, 0x20090810,
        0x00080020, 0x00080030, 0x20080020, 0x20080030,
        0x00090020, 0x00090030, 0x20090020, 0x20090030,
        0x00080820, 0x00080830, 0x20080820, 0x20080830,
        0x00090820, 0x00090830, 0x20090820, 0x20090830},
    /* for C bits (numbered as per FIPS 46) 7 8 10 11 12 13 */
    {
        0x00000000, 0x02000000, 0x00002000, 0x02002000,
        0x00200000, 0x02200000, 0x00202000, 0x02202000,
        0x00000004, 0x02000004, 0x00002004, 0x02002004,
        0x00200004, 0x02200004, 0x00202004, 0x02202004,
        0x00000400, 0x02000400, 0x00002400, 0x02002400,
        0x00200400, 0x02200400, 0x00202400, 0x02202400,
        0x00000404, 0x02000404, 0x00002404, 0x02002404,
        0x00200404, 0x02200404, 0x00202404, 0x02202404,
        0x10000000, 0x12000000, 0x10002000, 0x12002000,
        0x10200000, 0x12200000, 0x10202000, 0x12202000,
        0x10000004, 0x12000004, 0x10002004, 0x12002004,
        0x10200004, 0x12200004, 0x10202004, 0x12202004,
        0x10000400, 0x12000400, 0x10002400, 0x12002400,
        0x10200400, 0x12200400, 0x10202400, 0x12202400,
        0x10000404, 0x12000404, 0x10002404, 0x12002404,
        0x10200404, 0x12200404, 0x10202404, 0x12202404},
    /* for C bits (numbered as per FIPS 46) 14 15 16 17 19 20 */
    {
        0x00000000, 0x00000001, 0x00040000, 0x00040001,
        0x01000000, 0x01000001, 0x01040000, 0x01040001,
        0x00000002, 0x00000003, 0x00040002, 0x00040003,
        0x01000002, 0x01000003, 0x01040002, 0x01040003,
        0x00000200, 0x00000201, 0x00040200, 0x00040201,
        0x01000200, 0x01000201, 0x01040200, 0x01040201,
        0x00000202, 0x00000203, 0x00040202, 0x00040203,
        0x01000202, 0x01000203, 0x01040202, 0x01040203,
        0x08000000, 0x08000001, 0x08040000, 0x08040001,
        0x09000000, 0x09000001, 0x09040000, 0x09040001,
        0x08000002, 0x08000003, 0x08040002, 0x08040003,
        0x09000002, 0x09000003, 0x09040002, 0x09040003,
        0x08000200, 0x08000201, 0x08040200, 0x08040201,
        0x09000200, 0x09000201, 0x09040200, 0x09040201,
        0x08000202, 0x08000203, 0x08040202, 0x08040203,
        0x09000202, 0x09000203, 0x09040202, 0x09040203},
    /* for C bits (numbered as per FIPS 46) 21 23 24 26 27 28 */
    {
        0x00000000, 0x00100000, 0x00000100, 0x00100100,
        0x00000008, 0x00100008, 0x00000108, 0x00100108,
        0x00001000, 0x00101000, 0x00001100, 0x00101100,
        0x00001008, 0x00101008, 0x00001108, 0x00101108,
        0x04000000, 0x04100000, 0x04000100, 0x04100100,
        0x04000008, 0x04100008, 0x04000108, 0x04100108,
        0x04001000, 0x04101000, 0x04001100, 0x04101100,
        0x04001008, 0x04101008, 0x04001108, 0x04101108,
        0x00020000, 0x00120000, 0x00020100, 0x00120100,
        0x00020008, 0x00120008, 0x00020108, 0x00120108,
        0x00021000, 0x00121000, 0x00021100, 0x00121100,
        0x00021008, 0x00121008, 0x00021108, 0x00121108,
        0x04020000, 0x04120000, 0x04020100, 0x04120100,
        0x04020008, 0x04120008, 0x04020108, 0x04120108,
        0x04021000, 0x04121000, 0x04021100, 0x04121100,
        0x04021008, 0x04121008, 0x04021108, 0x04121108},
    /* for D bits (numbered as per FIPS 46) 1 2 3 4 5 6 */
    {
        0x00000000, 0x10000000, 0x00010000, 0x10010000,
        0x00000004, 0x10000004, 0x00010004, 0x10010004,
        0x20000000, 0x30000000, 0x20010000, 0x30010000,
        0x20000004, 0x30000004, 0x20010004, 0x30010004,
        0x00100000, 0x10100000, 0x00110000, 0x10110000,
        0x00100004, 0x10100004, 0x00110004, 0x10110004,
        0x20100000, 0x30100000, 0x20110000, 0x30110000,
        0x20100004, 0x30100004, 0x20110004, 0x30110004,
        0x00001000, 0x10001000, 0x00011000, 0x10011000,
        0x00001004, 0x10001004, 0x00011004, 0x10011004,
        0x20001000, 0x30001000, 0x20011000, 0x30011000,
        0x20001004, 0x30001004, 0x20011004, 0x30011004,
        0x00101000, 0x10101000, 0x00111000, 0x10111000,
        0x00101004, 0x10101004, 0x00111004, 0x10111004,
        0x20101000, 0x30101000, 0x20111000, 0x30111000,
        0x20101004, 0x30101004, 0x20111004, 0x30111004},
    /* for D bits (numbered as per FIPS 46) 8 9 11 12 13 14 */
    {
        0x00000000, 0x08000000, 0x00000008, 0x08000008,
        0x00000400, 0x08000400, 0x00000408, 0x08000408,
        0x00020000, 0x08020000, 0x00020008, 0x08020008,
        0x00020400, 0x08020400, 0x00020408, 0x08020408,
        0x00000001, 0x08000001, 0x00000009, 0x08000009,
        0x00000401, 0x08000401, 0x00000409, 0x08000409,
        0x00020001, 0x08020001, 0x00020009, 0x08020009,
        0x00020401, 0x08020401, 0x00020409, 0x08020409,
        0x02000000, 0x0A000000, 0x02000008, 0x0A000008,
        0x02000400, 0x0A000400, 0x02000408, 0x0A000408,
        0x02020000, 0x0A020000, 0x02020008, 0x0A020008,
        0x02020400, 0x0A020400, 0x02020408, 0x0A020408,
        0x02000001, 0x0A000001, 0x02000009, 0x0A000009,
        0x02000401, 0x0A000401, 0x02000409, 0x0A000409,
        0x02020001, 0x0A020001, 0x02020009, 0x0A020009,
        0x02020401, 0x0A020401, 0x02020409, 0x0A020409},
    /* for D bits (numbered as per FIPS 46) 16 17 18 19 20 21 */
    {
        0x00000000, 0x00000100, 0x00080000, 0x00080100,
        0x01000000, 0x01000100, 0x01080000, 0x01080100,
        0x00000010, 0x00000110, 0x00080010, 0x00080110,
        0x01000010, 0x01000110, 0x01080010, 0x01080110,
        0x00200000, 0x00200100, 0x00280000, 0x00280100,
        0x01200000, 0x01200100, 0x01280000, 0x01280100,
        0x00200010, 0x00200110, 0x00280010, 0x00280110,
        0x01200010, 0x01200110, 0x01280010, 0x01280110,
        0x00000200, 0x00000300, 0x00080200, 0x00080300,
        0x01000200, 0x01000300, 0x01080200, 0x01080300,
        0x00000210, 0x00000310, 0x00080210, 0x00080310,
        0x01000210, 0x01000310, 0x01080210, 0x01080310,
        0x00200200, 0x00200300, 0x00280200, 0x00280300,
        0x01200200, 0x01200300, 0x01280200, 0x01280300,
        0x00200210, 0x00200310, 0x00280210, 0x00280310,
        0x01200210, 0x01200310, 0x01280210, 0x01280310},
    /* for D bits (numbered as per FIPS 46) 22 23 24 25 27 28 */
    {
        0x00000000, 0x04000000, 0x00040000, 0x04040000,
        0x00000002, 0x04000002, 0x00040002, 0x04040002,
        0x00002000, 0x04002000, 0x00042000, 0x04042000,
        0x00002002, 0x04002002, 0x00042002, 0x04042002,
        0x00000020, 0x04000020, 0x00040020, 0x04040020,
        0x00000022, 0x04000022, 0x00040022, 0x04040022,
        0x00002020, 0x04002020, 0x00042020, 0x04042020,
        0x00002022, 0x04002022, 0x00042022, 0x04042022,
        0x00000800, 0x04000800, 0x00040800, 0x04040800,
        0x00000802, 0x04000802, 0x00040802, 0x04040802,
        0x00002800, 0x04002800, 0x00042800, 0x04042800,
        0x00002802, 0x04002802, 0x00042802, 0x04042802,
        0x00000820, 0x04000820, 0x00040820, 0x04040820,
        0x00000822, 0x04000822, 0x00040822, 0x04040822,
        0x00002820, 0x04002820, 0x00042820, 0x04042820,
        0x00002822, 0x04002822, 0x00042822, 0x04042822}};


/* The changes to this macro may help or hinder, depending on the
 * compiler and the achitecture.  gcc2 always seems to do well :-).
 * Inspired by Dana How <how@isl.stanford.edu>
 * DO NOT use the alternative version on machines with 8 byte longs. */

/* original version */
#define D_ENCRYPT(L, R, S)                  \
    u = (R ^ s[S]);                         \
    t = R ^ s[S + 1];                       \
    t = ((t >> 4) + (t << 28));             \
    L ^= des_SPtrans[1][(t)&0x3f] |         \
         des_SPtrans[3][(t >> 8) & 0x3f] |  \
         des_SPtrans[5][(t >> 16) & 0x3f] | \
         des_SPtrans[7][(t >> 24) & 0x3f] | \
         des_SPtrans[0][(u)&0x3f] |         \
         des_SPtrans[2][(u >> 8) & 0x3f] |  \
         des_SPtrans[4][(u >> 16) & 0x3f] | \
         des_SPtrans[6][(u >> 24) & 0x3f];

/* IP and FP
 * The problem is more of a geometric problem that random bit fiddling.
 0  1  2  3  4  5  6  7      62 54 46 38 30 22 14  6
 8  9 10 11 12 13 14 15      60 52 44 36 28 20 12  4
16 17 18 19 20 21 22 23      58 50 42 34 26 18 10  2
24 25 26 27 28 29 30 31  to  56 48 40 32 24 16  8  0

32 33 34 35 36 37 38 39      63 55 47 39 31 23 15  7
40 41 42 43 44 45 46 47      61 53 45 37 29 21 13  5
48 49 50 51 52 53 54 55      59 51 43 35 27 19 11  3
56 57 58 59 60 61 62 63      57 49 41 33 25 17  9  1

The output has been subject to swaps of the form
0 1 -> 3 1 but the odd and even bits have been put into
2 3    2 0
different words.  The main trick is to remember that
t=((l>>size)^r)&(mask);
r^=t;
l^=(t<<size);
can be used to swap and move bits between words.

So l =  0  1  2  3  r = 16 17 18 19
        4  5  6  7      20 21 22 23
        8  9 10 11      24 25 26 27
       12 13 14 15      28 29 30 31
becomes (for size == 2 and mask == 0x3333)
   t =   2^16  3^17 -- --   l =  0  1 16 17  r =  2  3 18 19
         6^20  7^21 -- --        4  5 20 21       6  7 22 23
        10^24 11^25 -- --        8  9 24 25      10 11 24 25
        14^28 15^29 -- --       12 13 28 29      14 15 28 29

Thanks for hints from Richard Outerbridge - he told me IP&FP
could be done in 15 xor, 10 shifts and 5 ands.
When I finally started to think of the problem in 2D
I first got ~42 operations without xors.  When I remembered
how to use xors :-) I got it to its final state.
*/
#define PERM_OP(a, b, t, n, m) ((t) = ((((a) >> (n)) ^ (b)) & (m)), \
                                (b) ^= (t),                         \
                                (a) ^= ((t) << (n)))


static unsigned char *key7TOkey8(const unsigned char *key7, unsigned char *key8)
{
    int i;

    key8[0] = ((key7[0] >> 1) & 0xff);
    key8[1] = ((((key7[0] & 0x01) << 6) | (((key7[1] & 0xff) >> 2) & 0xff)) & 0xff);
    key8[2] = ((((key7[1] & 0x03) << 5) | (((key7[2] & 0xff) >> 3) & 0xff)) & 0xff);
    key8[3] = ((((key7[2] & 0x07) << 4) | (((key7[3] & 0xff) >> 4) & 0xff)) & 0xff);
    key8[4] = ((((key7[3] & 0x0F) << 3) | (((key7[4] & 0xff) >> 5) & 0xff)) & 0xff);
    key8[5] = ((((key7[4] & 0x1F) << 2) | (((key7[5] & 0xff) >> 6) & 0xff)) & 0xff);
    key8[6] = ((((key7[5] & 0x3F) << 1) | (((key7[6] & 0xff) >> 7) & 0xff)) & 0xff);
    key8[7] = (key7[6] & 0x7F);

    for (i = 0; i < 8; i++) {
        key8[i] = (key8[i] << 1);
    }

    return (unsigned char *)key8;
}

static unsigned char DES_Keys[128] __attribute__((aligned(16)));

/*
 * des_create_keys: take 64bit user key (key) as input and outputs
 * 16 48bit keys (keys)
 */
static unsigned char *DES_createkeys(const unsigned char *key)
{
    unsigned int c, d, t;
    unsigned char *in;
    unsigned int *k;
    unsigned char k8[8];
    int i;
    static unsigned char shifts[16] = {0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0};

    key7TOkey8(key, k8);

    k  = (unsigned int *)DES_Keys;
    in = (unsigned char *)k8;

    c2l(in, c);
    c2l(in, d);

    /* I now do it in 47 simple operations :-)
     * Thanks to John Fletcher (john_fletcher@lccmail.ocf.llnl.gov)
     * for the inspiration. :-) */
    PERM_OP(d, c, t, 4, 0x0f0f0f0f);
    HPERM_OP(c, t, -2, 0xcccc0000);
    HPERM_OP(d, t, -2, 0xcccc0000);
    PERM_OP(d, c, t, 1, 0x55555555);
    PERM_OP(c, d, t, 8, 0x00ff00ff);
    PERM_OP(d, c, t, 1, 0x55555555);
    d = (((d & 0x000000ff) << 16) | (d & 0x0000ff00) |
         ((d & 0x00ff0000) >> 16) | ((c & 0xf0000000) >> 4));
    c &= 0x0fffffff;

    for (i = 0; i < ITERATIONS; i++) {
        unsigned int s;

        if (shifts[i]) {
            c = ((c >> 2) | (c << 26));
            d = ((d >> 2) | (d << 26));
        } else {
            c = ((c >> 1) | (c << 27));
            d = ((d >> 1) | (d << 27));
        }
        c &= 0x0fffffff;
        d &= 0x0fffffff;
        /* could be a few less shifts but I am to lazy at this
         * point in time to investigate */
        s = des_skb[0][(c)&0x3f] |
            des_skb[1][((c >> 6) & 0x03) | ((c >> 7) & 0x3c)] |
            des_skb[2][((c >> 13) & 0x0f) | ((c >> 14) & 0x30)] |
            des_skb[3][((c >> 20) & 0x01) | ((c >> 21) & 0x06) | ((c >> 22) & 0x38)];

        t = des_skb[4][(d)&0x3f] |
            des_skb[5][((d >> 7) & 0x03) | ((d >> 8) & 0x3c)] |
            des_skb[6][(d >> 15) & 0x3f] |
            des_skb[7][((d >> 21) & 0x0f) | ((d >> 22) & 0x30)];

        /* table contained 0213 4657 */
        *(k++) = ((t << 16) | (s & 0x0000ffff)) & 0xffffffff;
        s      = ((s >> 16) | (t & 0xffff0000));

        s      = (s << 4) | (s >> 28);
        *(k++) = s & 0xffffffff;
    }

    return (unsigned char *)DES_Keys;
}

unsigned char *DES(const unsigned char *key, const unsigned char *message, unsigned char *cipher)
{
    unsigned int l, r, t;
    int i;
    unsigned int *s;
    unsigned char *keys;

    keys = DES_createkeys(key);

    c2l(message, l); /* get endian free int from input block */
    c2l(message, r); /* get endian free int from input block */

    /* do IP */
    PERM_OP(r, l, t, 4, 0x0f0f0f0f);
    PERM_OP(l, r, t, 16, 0x0000ffff);
    PERM_OP(r, l, t, 2, 0x33333333);
    PERM_OP(l, r, t, 8, 0x00ff00ff);
    PERM_OP(r, l, t, 1, 0x55555555);
    /* r and l are reversed - remember that :-) - fix
     * it in the next step */

    /* Things have been modified so that the initial rotate is
     * done outside the loop.  This required the
     * des_SPtrans values in sp.h to be rotated 1 bit to the right.
     * One perl script later and things have a 5% speed up on a sparc2.
     * Thanks to Richard Outerbridge <71755.204@CompuServe.COM>
     * for pointing this out. */
    t = (r << 1) | (r >> 31);
    r = (l << 1) | (l >> 31);
    l = t;

    s = (unsigned int *)keys;
    /* I don't know if it is worth the effort of loop unrolling the
     * inner loop */
    for (i = 0; i < 32; i += 4) {
        unsigned int u;

        D_ENCRYPT(l, r, i + 0); /*  1 */
        D_ENCRYPT(r, l, i + 2); /*  2 */
    }
    l = (l >> 1) | (l << 31);
    r = (r >> 1) | (r << 31);

    /* swap l and r
     * we will not do the swap so just remember they are
     * reversed for the rest of the subroutine
     * luckily FP fixes this problem :-) */

    PERM_OP(r, l, t, 1, 0x55555555);
    PERM_OP(l, r, t, 8, 0x00ff00ff);
    PERM_OP(r, l, t, 2, 0x33333333);
    PERM_OP(l, r, t, 16, 0x0000ffff);
    PERM_OP(r, l, t, 4, 0x0f0f0f0f);

    l2c(l, cipher); /* get endian free int from input block */
    l2c(r, cipher); /* get endian free int from input block */

    return (unsigned char *)cipher;
}
